Semiconductor device performance can vary with changes to a number of different operating parameters. To increase yield and profit for a new device, it is desirable to verify, early on, that the manufacturing process used to produce the device reliably produces devices that are stable over a desired range of operating conditions. It is also useful for quality control during production to sample a fraction of devices to ensure that the manufacturing process continues to produce devices that are stable over the desired range of operating conditions. A test technique that can verify device stability over a range of conditions is commonly known as a “shmoo” or a “shmoo plot”.
Shmoo plots can be one-, two-, three-, or even N-dimensional. Each dimension of a shmoo plot represents one or more device parameters that is variable. Such device parameters may include device power supply voltage (Vdd), device clock frequency/period, and digital input or output voltage. However, any device parameters can be used to verify operation of the device or to identify problems with the device.
Test data, such as that used to generate a shmoo plot, may be obtained from automatic test equipment (ATE). ATE is an automated, usually computer-driven, system for testing devices, such as semiconductors, electronic circuits, and printed circuit board assemblies. A device tested by ATE is referred to as a device under test (DUT).